﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Workflows.Components.Entities.Documents.Terms
{
    /// <summary>
    /// Finding out the base form of a word, removing infexional endings
    /// Copyright (c) Martin Porter.
    /// </summary>
    public class PorterStemmer : IWordStemmer
    {
        private char[] _b;
        private int i,     // offset into b 
            i_end, // offset to end of stemmed word 
            j, k;
        private static int INC = 200;
        // unit of size whereby b is increased 

        public PorterStemmer()
        {
            _b = new char[INC];
            i = 0;
            i_end = 0;
        }

        public string StemTerm(string s)
        {
            setTerm(s);
            stem();
            return getTerm();
        }

        void setTerm(string s)
        {
            i = s.Length;
            char[] new_b = new char[i];
            for (int c = 0; c < i; c++)
                new_b[c] = s[c];

            _b = new_b;

        }

        public string getTerm()
        {
            return new String(_b, 0, i_end);
        }


        public void add(char ch)
        {
            if (i == _b.Length)
            {
                char[] new_b = new char[i + INC];
                for (int c = 0; c < i; c++)
                    new_b[c] = _b[c];
                _b = new_b;
            }
            _b[i++] = ch;
        }

        public void add(char[] w, int wLen)
        {
            if (i + wLen >= _b.Length)
            {
                char[] new_b = new char[i + wLen + INC];
                for (int c = 0; c < i; c++)
                    new_b[c] = _b[c];
                _b = new_b;
            }
            for (int c = 0; c < wLen; c++)
                _b[i++] = w[c];
        }

        public override string ToString()
        {
            return new String(_b, 0, i_end);
        }

        public int getResultLength()
        {
            return i_end;
        }

        public char[] getResultBuffer()
        {
            return _b;
        }


        private bool cons(int i)
        {
            switch (_b[i])
            {
                case 'a':
                case 'e':
                case 'i':
                case 'o':
                case 'u': return false;
                case 'y': return (i == 0) ? true : !cons(i - 1);
                default: return true;
            }
        }

        private int m()
        {
            int n = 0;
            int i = 0;
            while (true)
            {
                if (i > j) return n;
                if (!cons(i)) break; i++;
            }
            i++;
            while (true)
            {
                while (true)
                {
                    if (i > j) return n;
                    if (cons(i)) break;
                    i++;
                }
                i++;
                n++;
                while (true)
                {
                    if (i > j) return n;
                    if (!cons(i)) break;
                    i++;
                }
                i++;
            }
        }


        private bool vowelinstem()
        {
            int i;
            for (i = 0; i <= j; i++)
                if (!cons(i))
                    return true;
            return false;
        }


        private bool doublec(int j)
        {
            if (j < 1)
                return false;
            if (_b[j] != _b[j - 1])
                return false;
            return cons(j);
        }

        private bool cvc(int i)
        {
            if (i < 2 || !cons(i) || cons(i - 1) || !cons(i - 2))
                return false;
            int ch = _b[i];
            if (ch == 'w' || ch == 'x' || ch == 'y')
                return false;
            return true;
        }

        private bool ends(String s)
        {
            int l = s.Length;
            int o = k - l + 1;
            if (o < 0)
                return false;
            char[] sc = s.ToCharArray();
            for (int i = 0; i < l; i++)
                if (_b[o + i] != sc[i])
                    return false;
            j = k - l;
            return true;
        }

        /// setto(s) sets (j+1),...k to the characters in the string s, readjusting
        //
        private void setto(String s)
        {
            int l = s.Length;
            int o = j + 1;
            char[] sc = s.ToCharArray();
            for (int i = 0; i < l; i++)
                _b[o + i] = sc[i];
            k = j + l;
        }


        private void r(String s)
        {
            if (m() > 0)
                setto(s);
        }

        private void step1()
        {
            if (_b[k] == 's')
            {
                if (ends("sses"))
                    k -= 2;
                else if (ends("ies"))
                    setto("i");
                else if (_b[k - 1] != 's')
                    k--;
            }
            if (ends("eed"))
            {
                if (m() > 0)
                    k--;
            }
            else if ((ends("ed") || ends("ing")) && vowelinstem())
            {
                k = j;
                if (ends("at"))
                    setto("ate");
                else if (ends("bl"))
                    setto("ble");
                else if (ends("iz"))
                    setto("ize");
                else if (doublec(k))
                {
                    k--;
                    int ch = _b[k];
                    if (ch == 'l' || ch == 's' || ch == 'z')
                        k++;
                }
                else if (m() == 1 && cvc(k)) setto("e");
            }
        }


        private void step2()
        {
            if (ends("y") && vowelinstem())
                _b[k] = 'i';
        }

        private void step3()
        {
            if (k == 0)
                return;

            // For Bug 1 
            switch (_b[k - 1])
            {
                case 'a':
                    if (ends("ational")) { r("ate"); break; }
                    if (ends("tional")) { r("tion"); break; }
                    break;
                case 'c':
                    if (ends("enci")) { r("ence"); break; }
                    if (ends("anci")) { r("ance"); break; }
                    break;
                case 'e':
                    if (ends("izer")) { r("ize"); break; }
                    break;
                case 'l':
                    if (ends("bli")) { r("ble"); break; }
                    if (ends("alli")) { r("al"); break; }
                    if (ends("entli")) { r("ent"); break; }
                    if (ends("eli")) { r("e"); break; }
                    if (ends("ousli")) { r("ous"); break; }
                    break;
                case 'o':
                    if (ends("ization")) { r("ize"); break; }
                    if (ends("ation")) { r("ate"); break; }
                    if (ends("ator")) { r("ate"); break; }
                    break;
                case 's':
                    if (ends("alism")) { r("al"); break; }
                    if (ends("iveness")) { r("ive"); break; }
                    if (ends("fulness")) { r("ful"); break; }
                    if (ends("ousness")) { r("ous"); break; }
                    break;
                case 't':
                    if (ends("aliti")) { r("al"); break; }
                    if (ends("iviti")) { r("ive"); break; }
                    if (ends("biliti")) { r("ble"); break; }
                    break;
                case 'g':
                    if (ends("logi")) { r("log"); break; }
                    break;
                default:
                    break;
            }
        }

        // step4() deals with -ic-, -full, -ness etc. similar strategy to step3.
        private void step4()
        {
            switch (_b[k])
            {
                case 'e':
                    if (ends("icate")) { r("ic"); break; }
                    if (ends("ative")) { r(""); break; }
                    if (ends("alize")) { r("al"); break; }
                    break;
                case 'i':
                    if (ends("iciti")) { r("ic"); break; }
                    break;
                case 'l':
                    if (ends("ical")) { r("ic"); break; }
                    if (ends("ful")) { r(""); break; }
                    break;
                case 's':
                    if (ends("ness")) { r(""); break; }
                    break;
            }
        }

        // step5() takes off -ant, -ence etc., in context <c>vcvc<v>. 
        private void step5()
        {
            if (k == 0)
                return;

            // for Bug 1 
            switch (_b[k - 1])
            {
                case 'a':
                    if (ends("al")) break; return;
                case 'c':
                    if (ends("ance")) break;
                    if (ends("ence")) break; return;
                case 'e':
                    if (ends("er")) break; return;
                case 'i':
                    if (ends("ic")) break; return;
                case 'l':
                    if (ends("able")) break;
                    if (ends("ible")) break; return;
                case 'n':
                    if (ends("ant")) break;
                    if (ends("ement")) break;
                    if (ends("ment")) break;
                    // element etc. not stripped before the m 
                    if (ends("ent")) break; return;
                case 'o':
                    if (ends("ion") && j >= 0 && (_b[j] == 's' || _b[j] == 't')) break;
                    // j >= 0 fixes Bug 2 
                    if (ends("ou")) break; return;
                // takes care of -ous 
                case 's':
                    if (ends("ism")) break; return;
                case 't':
                    if (ends("ate")) break;
                    if (ends("iti")) break; return;
                case 'u':
                    if (ends("ous")) break; return;
                case 'v':
                    if (ends("ive")) break; return;
                case 'z':
                    if (ends("ize")) break; return;
                default:
                    return;
            }
            if (m() > 1)
                k = j;
        }

        // step6() removes a final -e if m() > 1. 
        private void step6()
        {
            j = k;

            if (_b[k] == 'e')
            {
                int a = m();
                if (a > 1 || a == 1 && !cvc(k - 1))
                    k--;
            }
            if (_b[k] == 'l' && doublec(k) && m() > 1)
                k--;
        }

        public void stem()
        {
            k = i - 1;
            if (k > 1)
            {
                step1();
                step2();
                step3();
                step4();
                step5();
                step6();
            }
            i_end = k + 1;
            i = 0;
        }


    }
}
